This is a "witch's broom" growing off a White Fir. Although it looks extremely different from the rest of the tree, it is not an external organism like a mistletoe. Instead, it is an unusual growth like a gall that could have been triggered by any one of a number causes, including mites, fungi, mistletoes, nematodes, phytoplasmas, or viruses.
Overlook above Idyllwild
Abies concolor, commonly known as the white fir, is a fir native to the mountains of western North America, occurring at elevations of 900–3,400 m (2,952–11,154 ft). It is a medium to large evergreen coniferous tree growing to 25–60 m (80–197 ft) tall and with a trunk diameter of up to 2 m (6.5 ft). It is popular as an ornamental landscaping tree and as a Christmas tree. It is sometimes known as concolor fir.